A car travels at a speed of 25 m/s on a flat stretch of road. The driver must maitain pressure on the accelerator to keep the car moving at a constant speed.

Question

Are there any forces doing work on the car? Explain.
What is the net force?

Answer 1

The net force is zero.

The engine does work on the car, by applying a torque to the drive shaft. The work is necessary to overcome aerodynamic and internal (engine and bearing) friction.

The road applies a force to the tires to keep the car moving forward, but the road does not do work. The work is generated internally by the engine.